Missouri University. US: babies in what researchers call their “prelinguistic period” can’t form words, but they have plenty of important things to say. Gurgling, cooing, babbling: These, and other forms of vocalization, all precede and are thought to play a role in the development of fully formed speech.
But what about infants who can’t hear themselves make these sounds? Perhaps not surprisingly, says an MU researcher, infants who can’t discern their own baby talk face a tougher road to speech formation.
MU’s Mary Fagan is working to change that. An assistant professor of communication science and speech disorders, Fagan’s recent research has shown that infant vocalizations are primarily motivated by infants’ ability to hear their own voices.
For those with profound hearing loss, Fagan discovered, the inability to benefit from this “auditory feedback” is likely one root of their language-related difficulties.
Fortunately, her study also determined that timely intervention can make a big difference, helping infants reach the vocalization levels of their hearing peers and putting them on track for language development.
“Hearing is a critical aspect of infants’ motivation to make early sounds,” says Fagan. “This study shows babies are interested in speech-like sounds and that they increase their babbling when they can hear.”
Fagan studied the vocalizations of 27 hearing infants and 16 infants with profound hearing loss who were candidates for cochlear implants — those tiny electronic devices that, when embedded into the bone behind the ear, can replace some functions of the damaged inner ear.
She determined, in results published in in the June 2014 issue of the Journal of Experimental Child Psychology, that infants with profound hearing loss vocalized significantly less than hearing babies.
After receiving cochlear implants, however, the recipients’ vocalizations increased to the same levels as their hearing peers within the span of just four months. “These findings support the importance of early hearing screenings and early cochlear implantation,” she says.
Fagan also discovered that non-speech-like sounds such as crying, laughing and “raspberry” sounds were not affected by infants’ hearing ability. This finding highlights, she says, the fact that babies are more interested in making hearing-dependent “speech-like” sounds.
“Babies learn so much through sound in the first year of their lives,” Fagan says. “We know learning from others is important to infants’ development, but hearing allows infants to explore their own vocalizations and learn through their own capacity to produce sounds.”